recurring shift issues. on 1993 Dodge Dakota

Problem first occured when rear differential seiezed. Replaced rear, and no problems till oneday I noticed a noise and vibration from right below my feet at 60+mph. Then it started shifting weird. 1-2 shift fine but it would almost immediatly shift into 3rd and slip while doing so. So I replaced the transmission and the noise and vibration above 60mph is gone, but it still shifts weird. Same exact shift problems. Like it building up line pressure too quick in 2nd. When I hold it in 2nd with te shifter, and shift into 3rd(drive) at normal shift point it shifts fine, no slip or anything. So I'm lead to believe its not the trans. My truck has the chyrsler A-500 auto and last I knew it was all hydraulically controlled. The only elctronics on it were for O/D. But would a plugged cooler cause this shifting issue? Other than that transmission is great all gears work perfectly except the way short slippage into 3rd. Any help would be greatly appreciated. Thanks in advanced. Chris

Transmission throttle valve cable adjustment is extremely important to proper operation. This adjustment positions the throttle valve, which controls shift speed, quality, and part-throttle downshift sensitivity.
If cable setting is too loose, early shifts and slippage between shifts may occur. If the setting is too tight, shifts may be delayed and part throttle downshifts may be very sensitive.
TRANSMISSION THROTTLE VALVE CABLE ADJUSTMENT
The transmission throttle valve is operated by the valve body throttle lever. The throttle lever is actuated by a cable connected to the engine throttle body lever A lock button at the engine end of the cable provides for cable adjustment. A correctly adjusted throttle valve cable, will cause the throttle lever on the transmission to move simultaneously with the throttle body lever from the idle position. Proper adjustment allows simultaneous movement without causing the transmission throttle lever to move ahead of, or lag behind the throttle body lever.
THROTTLE VALVE CABLE ADJUSTMENT PROCEDURE
1.Turn ignition switch to OFF position and shift into Park.
2.Remove air cleaner.
3.Disconnect cable end from attachment stud on throttle body.
4.Verify that transmission throttle lever is in idle (full forward) position. Then be sure lever on throttle body is at curb idle position.
5.Insert a small screwdriver under edge of retaining clip and remove retaining clip.
6.Center cable end on attachment stud to within 1 mm (0.039 in.) and release cable button.
7.Install retaining clip onto cable housing.
8.Check cable adjustment. Be sure transmission throttle lever and lever on throttle body move simultaneously and as described in cable adjustment checking procedure.